I'm not sure your position is consistent, since, if the TSA is filling the role that private security used to fill, there must be some explanation for the change, and the TSA was created in direct response to the 9/11 attacks. (I'm not even sure sentiment would have been in a place to create something like the TSA without 9/11 either.)
However, my point wasn't whether the TSA was created specifically for one type of attack, but that it was created for a problem that 90% solved to begin with and the remaining 10% could have been filled with government serving as intelligence and advisor (e.g. requiring airlines to reinforce cockpit doors, or informing them of specific plots or new techniques to defend against); which, of course, it was failing to do pre-9/11, but that's a separate problem also not solved by the TSA.
I don't think that is true. Maybe the threat of kamikaze hijackings was behind some of the push, but it is far from the only reason.
Plus TSA isn't all that different from the old private security guard system we used have have pre-911. The extra screenings are entirely related to specific bomb--not hijacking--threats. Shoes off? because of the shoe bomber. No liquids because of the liquid bomb plot.